Fused substrate resistor

ABSTRACT

A capless electroconductive coating resistor. The resistor dielectric substrate is formed of particulate material by pressing or molding within which substrate wire leads are embedded. The green body so formed is fired to coalesce or sinter the particles and volatilize any organic constituents. Thereafter, an electroconductive coating is applied over the surface of the substrate in electrical contact with the leads.

Uited States Patent Inventor Guenter H. Loose Webster, N.Y.

Appl. No. 44,236

Filed June .8, 1970 Patented Dec. 7, 1971 v Assignee Corning Glass Works Corning, NY.

Original application Dec. 27, 1968, Ser. No. 787,312. Divided and this application June 8, 1970, Ser. No. 44,236

FUSED SUBSTRATE RESISTOR 5 Claims, 5 Drawlng Figs.

[1.8. Ci 338/263, 338/276, 338/300, 338/3l2, 338/33l Int. Cl ll-l0lc 1/14 Field of Search 338/312,

[56] References Cited UNITED STATES PATENTS 2,742,551 4/1956 Kohring 317/312 Primary Examiner-E. A. Goldberg An0rneysClarence R. Patty, Jr. and Walter S. Zebrowski ABSTRACT: A capless electroconductive coating resistor. The resistor dielectric substrate is formed of particulate material by pressing or molding within which substrate wire leads are embedded. The green body so formed is fired to coalesce or sinter the particles and volatilize any organic constituents. Thereafter, an electroconductive coating is applied over the surface of the substrate in electrical contact with the leads.

PATENTEDDEC TIIITI 1626353 SHEET 1 0F 2 GLASS PARTICLE A 'WIRE LEAD FEED FEED MOLD OR PRESS RESISTOR SUBSTRATE AND LEADS FIRE SUBSTRATE WITH LEADS (SINTER).

, APPLY ELEcTRocDNDucTIv APPLY CONDUCTNE T' I COATING TO THE,

JUNCTION BETWEEN LEADS a ELECTRO- coNDucTIvE COAT- CLEAN AND ING IF DESIRED TIN LEADS SPIRAL ELECTRO- T CONDUCTIVE coAT- lNG IF DESIRED ENCAPSULATE I COAT 0 OTHERWISE FINISH RESISTOR INVENTOR. Guenfer H. Loose ATTORNEY PATENTEU DEC 1 an SHEET 2 [1F 2 INVENTOR. Guenfer H. Loose ATTORNEY russn sunsraxrr: RESISTOR CROSS-REFERENCE TO RELATED APPLICATION This application is a division of application Ser. No. 787,3l 2,file'd Dec. 27, I968.

BACKGROUND OF THE INVENTION Resistors having electroconductive coatings have heretofore been made by forming a dielectric resistor substrate, ordinarily in cylindrical shape. applying thereto a film of electroconductive or resistive material, and thereafter cutting the dielectric substrate into individual resistor blanks. The resistor blanks would have a coating of silver or other conductive material applied to the ends thereof, be fired to fuse the conductive material, and the blanks would thereafter be spiralled if desired to increase the resistance value thereof. A metallic cap with a lead attached thereto would be fitted over the ends of the resistor blanks so that electrical contact could be made between the lead and the electroconductive or resistive material through said conductive material. The resistor would then be suitably coated or encapsulated. Such a method would require the diameter of the dielectric substrate to be maintained within close tolerances so that caps could thereafter be properly fitted onto the ends thereof. The lead and cap combinations result in an expensive means for providing electrical continuity between the electroconductive coating and the leads. In addition, the caps increase the diameter of overall device. Furthermore, the method requires expensive capping machines to fit the caps over the ends of the resistor blanks and cutoff machines for cutting off individual resistor blanks from the continuous substrate material.

SUMMARY OF THE INVENTION The objects of the present invention are to provide a simplified, direct, and inexpensive method of manufacturing electroconductive coating or film resistors which are capless, rugged, and inexpensive and which overcome the hereinabove-noted disadvantages.

Briefly, according to the present invention, a capless electroconductive coating resistor can be formed by first pressing or molding a quantity of particulate dielectric material within which wire leads are embedded to form a resistor blank. The green body so formed is fired to coalesce or sinter the particles forming a cohesive substrate for the resistor and to volatilize any organic constituents. Thereafter an electroconductive or resistive coating is applied over the surface of the substrate in contact with the leads. The resistor so constructed may have conductive material applied at the ends of the resistor body to improve the electrical conductivity between the leads and the electroconductive coating. Thereafter, the leads may be cleaned and tinned, the electroconductive material spiralled to increase the resistance thereof, and the resistor encapsulated, coated or otherwise finished.

Additional objects, features, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description and the attached drawings on which, by way of example, only the preferred embodiment of thisinvention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow diagram illustrating the process of the present invention.

FIG. 2 is a fragmentary elevation of an apparatus for pressing resistor blanks of the present invention.

FIG. 3 is a cross-sectional elevation of a resistor blank of the present invention.

FIG. 4 is a cross-sectional elevation of a resistor blank of the present invention having an electroconductive coating applied to the surfaces thereof.

FIG. 5 is a cross-sectional elevation of the resistor blank of FIG. 4 having a coating of conductive material applied to the ends thereof.

DETAILED DESCRIPTION F th purp s s o s mp c ty. he presen nven ion wi l be described i o e tio with fo m ng a capless es stor ha i s a glass d e tr an an elect o o ductive oating cf m ta oxide. As is readily understood the present invention is in no ay t d to such mate i s- D ele tr mate ia s suitable for t e p s pu pose m y be glass. glass ceramics, ceramic plastics, and the like. For a clear understanding of metallic xid films s e ect oco ducti coatings. eir ch race i ic an a as one example f the r applica i n. reference is made to U.S. Pat. Nos. 2,564,706 and 2,564,707 issued o John M- Mcchel. th d closure of wh h patent is incorporated herein by reference.

Referring to FIG. 1, there is shown a flow diagram of the m h of h pr sen nven ion Refe r ng ad i ionally o FIG. 2 there is shown an apparatus 10 by which resistor blanks 12 may be pressed or molded. A pair of forming wheels 14 and 16 have, about the periphery thereof, a plurality of matching recesses, cavities, or mold compartments I8. Forming wheels 14. and 16 are aligned so that the mold compartments I8, substantially form cylindrical cavities at the point where the wheels are tangent to one another. Wheels 14 and 16 may be driven by any suitable driving means, not shown, well known in the art. Resistor leads 20 are positioned about the periphery of forming wheel 16 by means of a lead feed device 22. The leads are positioned so that a portion of one end thereof extends into cavity 18. Suitable lead materials are copper. Dumet, Kovar, nickel, or the like, and one familiar with the art can readily select a suitable lead material for a particular application. Particulate dielectric material is fed to mold compartments 18 by means of a dielectric material feed mechanism 24. As is readily understood, lead feed device 22 and dielectric material feed mechanism 24 may be any suitable feed devices well known in the art, and no particular device or feed means ar o template r for pa o th present invention. The particulate material is fed to mold compartments 18 at such a rate and at a time before the particular mold compartments are caused to be in register with one another at the point where forming wheels 14 and 16 are tangent to one another. By providing a proper amount of dielectric material to the mold cavities the forming wheels will cause the dielectric material to be compressed thereby forming a cylindrical shape having a lead 20 embedded in each end thereof forming green resistor blanks 1 2 In order that sufficient green strength is obtained in the compressed resistor n a binder i added to h p rticu a e die ec ric materia Such a binder may be organic materials such as starch, glycerin. e hyle e g yc ell e n t a cell lo e acet amyl and butyl alcohols, paraffin, polyethylene glycol or the like. The binder is added in quantities Suf ic ent to provide green strength of a desired value in the resistor blank.

The green resistor blanks are then fired to volatilize the or: ganic constituents, coalesce or sinter the particles of dielectric material forming a cohesive substrate for a resistor, and to bond the leads firmly thereto as illustrated in FIG. 3.

Thereafter, an electroconductive coating 26, such as the metallic oxide films of the heretofore noted Mochel patents is applied over the surface of the substrate or blank 12 in electrical contact with leads 20 as illustrated in FIG. 4.

The resistor so constructed may thereafter have a conduc tive material 28 applied at the ends of the resistor body and to the junction between the leads and the electroconductive coating to ensure electrical conductivity therebetween. Coating 28 may be any highly conductive material such as Silver, conductive frit, conductive paint, conductive plastic, or the like. Conductive material 28 is illustrated in exaggeratedthickness in FIG. 5 and is merely a coating or film.

Leads 20 of a resistor so formed, are thereafter suitably cleaned and tinned by any method well known in the art.

Coating 26 may be spiralled to increase the length to width As a typical example a quantity of particulate glass having a composition by weight of 60% SiO 15% A1 l0% C210, 5% MgO, 5% BaO, and 5% 8 0 to which was added polyethylene glycol as a binder, was compressed within a mold to form a cylindrical resistor blank having a copper wire lead embedded in each end thereof. The binder comprised about 2 percent by weight of the total material. The green resistor blank was then fired to volatilize the organic constituents and to coalesce or sinter the particles in accordance with the following schedule: 350 C. for l8 minutes, 450 C. for 18 minutes, and 900 C. for 18 minutes. The resistor blank was cooled and a coating of thin and antimony oxide was applied to the outer surface of the blank and in contact with the leads in accordance with the method taught by the heretofore-noted Mochel patents. The tin and antimony oxide film was spiralled to increase the resistance thereof and the completed assembly was coated with an encapsulating resin.

Although the present invention has been described with respect to specific details of certain embodiments thereof, it is not intended that such details be limitations upon the scope of the invention except insofar as set forth in the following claims.

I claim:

1. A capless electroconductive coating resistor comprising a substantially cylindrical dielectric substrate formed of sin tered particulate glass,

a wire lead embedded in each end of said substrate and bonded thereto along the longitudinal axis thereof, and

a coating of electroconductive material applied to the surface of said substrate and a portion of said leads whereby electrical contact is made between said leads and said coating, the electroconductive coating only forming the resistive path of said resistor.

2. The resistor of claim 1 further comprising a coating of highly conductive material disposed at the junction between said coating of electroconductive material and said leads.

3. The resistor of claim 1, wherein said coating of electroconductive material is spiralled.

4. The resistor of claim I further comprising a coating of an encapsulant material applied to the outer surface of the structure so formed.

5. The resistor of claim 3 wherein said highly conductive material is silver.

l l l 

1. A capless electroconductive coating resistor comprising a substantially cylindrical dielectric substrate formed of sintered particulate glass, a wire lead embedded in each end of said substrate and bonded thereto along the longitudinal axis thereof, and a coating of electroconductive material applied to the surface of said substrate and a portion of said leads whereby electrical contact is made between said leads and said coating, the electroconductive coating only forming the resistive path of said resistor.
 2. The resistor of claim 1 further comprising a coating of highly conductive material disposed at the junction between said coating of electroconductive material and said leads.
 3. The resistor of claim 1, wherein said coating of electroconductive material is spiralled.
 4. The resistor of claim 1 further comprising a coating of an encapsulant material applied to the outer surface of the structure so formed.
 5. The resistor of claim 3 wherein said highly conductive material is silver. 